This lecture was conducted during the
Nephrology Unit Grand Ground by Medical
Student rotated under Nephrology Division
under the supervision and administration of
Prof. Jamal Al Wakeel, Head of Nephrology
Unit, Department of Medicine and Dr.
Abdulkareem Al Suwaida, Chairman of the
Department of Medicine. Nephrology Division is
not responsible for the content of the
presentation for it is intended for learning and
/or education purpose only.
MYASTHENIA GRAVIS
Presented by:
Fayez Al Rogi
Medical Student
February 2009
DEFINITION
• Chronic autoimmune neuromuscular
disease.
• It is a disorder of neuromuscular function
thought to be due to the presence of
antibodies to acetylcholine receptors at
the neuromuscular junction.
PREVALENCE
• Prevalence of 50,000 cases in US.
• All ethnic groups and both genders.
• Female to male ratio
– 20 to 40 years (females 1.5:1)
– 50 to 70 years (males 1.5:1)
IMMUNOPATHOLOGY
• Autoantibody (antagonistic) for
acetylcholine receptor at post-synaptic
neuromuscular junction.
• The nerve cell conveys its message to tell
the muscle to contract. The antibodies
interfere with the message and the
muscle contracts less efficiently. Resulting
in the weakness of the arms or legs or of
the muscles of the head.
• Acetylcholine receptors are
– Blocked
– Altered
– Destroyed
• 75% of patients have thymus abnormality:
– 85% thymic hyperplasia
– 15% thyroma
– Disease usually more severe with thymus
abnormality.
ETIOLOGY
• The cause is unkown.
CLINICAL FEATURES
• Drooping of the eyelids (Ptosis).
• Double vision.
• Facial muscles weakness.
• Difficulty in swallowing (dysphagia).
• Weakness of arms, hands, fingers, legs.
• Difficulty breathing if chest muscle are
affected.
Diplopia Ptosis
Exacerbation of MG
• Emotional stress
• Pregnancy
• Menses
• Secondary illness
• Trauma
• Temperature extremes
• Hypokalemia
• Drugs – aminoglycosides antibiotics, beta
blockers, procainamide, quinidine,
phentoin, and some psychotropic drugs
DIAGNOSIS OF MG
• History.
• Physical examinations for muscle
fatigue.
• Edrophonium Test.
• EMG.
• Lab Dx.
• CT of thymus gland.
Edrophonium Test (Tensilon)
– IV administration of Edrophonium
chloride
– Blocks degradation of acetylcholine
– Brief relief of eye weakness
Laboratory Dx
Acetylcholine receptor antibody (Anti-AChR)
• Acetylcholine receptor antibody, binding
– 90% generalized
– 70% ocular
• Acetylcholine receptor antibody, blocking
– 50% generalized
– 20% ocular
• Acetylcholine receptor antibody, modulating
– 90% generalized
– 70% ocular
Muscle-specific tyrosine kinase antibody
– Anti-MuSK
– 45% of seronegative MG
TREATMENT
• Anticholinesterase agents
– Neostigmine (Prostigmin)
– Pyridostigmine (Mestinon)
• Corticosteroids / Immunosuppressive
agents
– Prednisone
– Azathioprine
• Intravenous Immunoglobulin (IVIG)
• Thymectomy
• Plasmapheresis (plasma exchange)
LIFESTYLES
• A person with Myasthenia Gravis can
lead a normal life if the medications
are taken in the correct dosages and
at the right time of the day.
THANK YOU